Our long term objective is to contribute to a better understanding of the cellular role in mineralization. The distribution and movements of calcium in and between cells associated with mineralizing enamel and dentin currently remain elusive. One approach to this problem is to investigate membrane-associated enzymes which may influence the movements of calcium ions during mineralization. Certain phosphatases present in secretory and non-secretory ameloblasts and odontoblasts of frogs teeth are being localized by light and electron microscopic cytochemistry and assayed biochemically during different stages of amelogenesis and dentinogenesis. A second approach to this problem is to diresctly or indirectly localize calcium in the tissues. Autoradiography of Ca-45, calcium precipitation with potassium pyroantimonate, x-ray dispersive analysis, and electron energy loss spectroscopy have been employed to study the distribution of calcium in incisors of normal and experimentally treated rats.